can't free dragon from trap??? says talk to him not talking ???

to release him you need to take the stairs to the upper level and pull the lever. should be on your right hand side if your back is to the door and your facing the dragon.

Go to Dragonsreach to prepare and spring the trap with the help of Jarl Balgruuf or Jarl Vignar Gray-Mane, depending on the current allegiance of Whiterun. The area you need to go is located behind the throne room and up the stairs (you can just follow the jarl). Tell the jarl you're ready, then use the Call Dragon shout by holding it down for a moment. Odahviing will appear after a short delay and attack, being curious to test your power. Fight him, and draw him closer to the doors you came in through using the shout Dragonrend. Climb the stairs that start near the doors, or simply back up towards the rear of the room, and a large wooden yoke will drop down and snap around his neck, holding him in place. You can then interrogate him and he will start talking to you.

He will tell you where Alduin has gone; a former temple of the Dragon Cult called Skuldafn Temple. Interrogate him further and he will reveal to you that it is impossible to get to Skuldafn without wings, but he will take you if you release him. Before you accept his offer, make sure you have everything you need for a long mission, as you will not be able to leave Skuldafn until after you have completed the next three quests. You cannot take any followers with you to Skuldafn. When you are ready, talk to a guard on the upper level to release Odahviing. He will not fly away, so talk to the now-freed Odahviing for the flight to Skuldafn.